Need help with javascript and local storage

I need help with my file, I am creating a movie database and one of my tasks requires me to create a “watched” button on my watchlist, now the problem is that when i tag one movie as watched, they all get tagged as watched because they share a button, but i can’t make it so that they dont share a button because the button is created every time a new movie gets added to a watchlist, is there any way what so ever to make it so that only one button at a time gets tagged, and stays that way when the page is reloaded? Any help would be appriciated! 

Here are the files and codes (it’s not a very long list of codes) 

https://github.com/karlokralj/halp